Add unit tests for FSTIndexHandler legacy-FST detection and index lifecycle

pinot-segment-local/src/test/java/org/apache/pinot/segment/local/segment/index/loader/invertedindex/FSTIndexHandlerTest.java

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+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.pinot.segment.local.segment.index.loader.invertedindex;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.TreeSet;
+import org.apache.commons.io.FileUtils;
+import org.apache.pinot.segment.local.segment.creator.impl.SegmentIndexCreationDriverImpl;
+import org.apache.pinot.segment.local.segment.readers.GenericRowRecordReader;
+import org.apache.pinot.segment.local.segment.store.SegmentLocalFSDirectory;
+import org.apache.pinot.segment.spi.ColumnMetadata;
+import org.apache.pinot.segment.spi.V1Constants;
+import org.apache.pinot.segment.spi.creator.SegmentGeneratorConfig;
+import org.apache.pinot.segment.spi.creator.SegmentVersion;
+import org.apache.pinot.segment.spi.index.FieldIndexConfigs;
+import org.apache.pinot.segment.spi.index.FstIndexConfig;
+import org.apache.pinot.segment.spi.index.StandardIndexes;
+import org.apache.pinot.segment.spi.index.metadata.SegmentMetadataImpl;
+import org.apache.pinot.segment.spi.memory.PinotDataBuffer;
+import org.apache.pinot.segment.spi.store.SegmentDirectory;
+import org.apache.pinot.spi.config.table.TableConfig;
+import org.apache.pinot.spi.config.table.TableType;
+import org.apache.pinot.spi.data.FieldSpec;
+import org.apache.pinot.spi.data.Schema;
+import org.apache.pinot.spi.data.readers.GenericRow;
+import org.apache.pinot.spi.utils.ReadMode;
+import org.apache.pinot.spi.utils.builder.TableConfigBuilder;
+import org.testng.annotations.Test;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+import static org.testng.Assert.assertFalse;
+import static org.testng.Assert.assertThrows;
+import static org.testng.Assert.assertTrue;
+
+
+/// Unit tests for [FSTIndexHandler].
+///
+/// Covers:
+/// - needUpdateIndices returns true when legacy native FST is detected (triggers rebuild)
+/// - updateIndices removes the legacy native FST index
+/// - needUpdateIndices returns true when a column is dropped from the FST index config
+/// - updateIndices removes the on-disk index when a column is dropped from config
+/// - needUpdateIndices returns true when a new column is added to the config
+/// - needUpdateIndices returns false when the index is already present and matches config
+/// - needUpdateIndices throws UnsupportedOperationException for non-STRING, no-dict, or MV columns
+/// - updateIndices creates a new FST index file for a newly configured column
+public class FSTIndexHandlerTest {
+  private static final String COLUMN = "name";
+
+  /**
+   * Magic int written at offset 0 of every legacy native FST file.
+   * Mirrors the private constant in {@code FstIndexUtils}.
+   */
+  private static final int LEGACY_NATIVE_FST_MAGIC = ('\\' << 24) | ('f' << 16) | ('s' << 8) | 'a';
+
+  /** [FieldIndexConfigs] with FST explicitly disabled — used in removed-column tests. */
+  private static final FieldIndexConfigs NO_FST =
+      new FieldIndexConfigs.Builder().add(StandardIndexes.fst(), FstIndexConfig.DISABLED).build();
+
+  @Test
+  public void testNeedUpdateReturnsTrueWhenLegacyNativeFstDetected()
+      throws Exception {
+    SegmentDirectory segmentDirectory = mockSegmentDirectory(COLUMN);
+    SegmentDirectory.Reader reader = mockReaderWithFstBuffer(segmentDirectory, COLUMN, legacyNativeBuffer());
+
+    FSTIndexHandler handler = createHandler(segmentDirectory);
+
+    assertTrue(handler.needUpdateIndices(reader),
+        "Rebuild expected when legacy native FST index is detected");
+  }
+
+  @Test
+  public void testUpdateIndicesRemovesLegacyNativeFstIndex()
+      throws Exception {
+    SegmentDirectory segmentDirectory = mockSegmentDirectory(COLUMN);
+    SegmentDirectory.Writer writer = mockWriterWithFstBuffer(segmentDirectory, COLUMN, legacyNativeBuffer());
+
+    FSTIndexHandler handler = createHandler(segmentDirectory);
+    handler.updateIndices(writer);
+
+    verify(writer).removeIndex(COLUMN, StandardIndexes.fst());
+  }
+
+  @Test
+  public void testNeedUpdateReturnsTrueWhenColumnRemovedFromConfig()
+      throws Exception {
+    // Column has an FST index on disk but the new config has no FST index for it.
+    SegmentDirectory segmentDirectory = mockSegmentDirectory(COLUMN);
+    SegmentDirectory.Reader reader = mockReaderWithFstBuffer(segmentDirectory, COLUMN, nonLegacyBuffer());
+
+    FSTIndexHandler handler = new FSTIndexHandler(segmentDirectory, Map.of(COLUMN, NO_FST),
+        mock(TableConfig.class), mock(Schema.class));
+
+    assertTrue(handler.needUpdateIndices(reader),
+        "Rebuild expected to remove index when column is dropped from FST index config");
+  }
+
+  @Test
+  public void testUpdateIndicesRemovesIndexWhenColumnDroppedFromConfig()
+      throws Exception {
+    SegmentDirectory segmentDirectory = mockSegmentDirectory(COLUMN);
+    SegmentDirectory.Writer writer = mockWriterWithFstBuffer(segmentDirectory, COLUMN, nonLegacyBuffer());
+
+    FSTIndexHandler handler = new FSTIndexHandler(segmentDirectory, Map.of(COLUMN, NO_FST),
+        mock(TableConfig.class), mock(Schema.class));
+    handler.updateIndices(writer);
+
+    verify(writer).removeIndex(COLUMN, StandardIndexes.fst());
+  }
+
+  @Test
+  public void testNeedUpdateReturnsTrueWhenNewColumnAdded()
+      throws Exception {
+    // Column is in config but has no existing FST index.
+    SegmentMetadataImpl segmentMetadata = mock(SegmentMetadataImpl.class);
+    when(segmentMetadata.getName()).thenReturn("testSegment");
+    when(segmentMetadata.getTotalDocs()).thenReturn(1);
+    when(segmentMetadata.getAllColumns()).thenReturn(new TreeSet<>(Set.of(COLUMN)));
+    ColumnMetadata columnMetadata = mock(ColumnMetadata.class);
+    when(columnMetadata.getColumnName()).thenReturn(COLUMN);
+    when(columnMetadata.getDataType()).thenReturn(FieldSpec.DataType.STRING);
+    when(columnMetadata.hasDictionary()).thenReturn(true);
+    when(columnMetadata.isSingleValue()).thenReturn(true);
+    when(segmentMetadata.getColumnMetadataFor(COLUMN)).thenReturn(columnMetadata);
+
+    SegmentDirectory segmentDirectory = mock(SegmentDirectory.class);
+    when(segmentDirectory.getSegmentMetadata()).thenReturn(segmentMetadata);
+    when(segmentDirectory.getColumnsWithIndex(StandardIndexes.fst())).thenReturn(Set.of());
+
+    SegmentDirectory.Reader reader = mock(SegmentDirectory.Reader.class);
+    when(reader.toSegmentDirectory()).thenReturn(segmentDirectory);
+
+    FSTIndexHandler handler = createHandler(segmentDirectory);
+
+    assertTrue(handler.needUpdateIndices(reader),
+        "New FST index expected for column added to config");
+  }
+
+  @Test
+  public void testNeedUpdateReturnsFalseWhenIndexUpToDate()
+      throws Exception {
+    // Column has a Lucene FST index, is in config, and the buffer is not a legacy native index.
+    SegmentDirectory segmentDirectory = mockSegmentDirectory(COLUMN);
+    SegmentDirectory.Reader reader = mockReaderWithFstBuffer(segmentDirectory, COLUMN, nonLegacyBuffer());
+
+    FSTIndexHandler handler = createHandler(segmentDirectory);
+
+    assertFalse(handler.needUpdateIndices(reader),
+        "No rebuild expected when FST index is current and matches config");
+  }
+
+  @Test
+  public void testNeedUpdateThrowsForNonStringColumn()
+      throws Exception {
+    SegmentDirectory segmentDirectory = mockSegmentDirectoryForNewColumn(FieldSpec.DataType.INT, true, true);
+    SegmentDirectory.Reader reader = mock(SegmentDirectory.Reader.class);
+    when(reader.toSegmentDirectory()).thenReturn(segmentDirectory);
+
+    FSTIndexHandler handler = createHandler(segmentDirectory);
+
+    assertThrows(UnsupportedOperationException.class, () -> handler.needUpdateIndices(reader));
+  }
+
+  @Test
+  public void testNeedUpdateThrowsWhenNoDictionary()
+      throws Exception {
+    SegmentDirectory segmentDirectory = mockSegmentDirectoryForNewColumn(FieldSpec.DataType.STRING, false, true);
+    SegmentDirectory.Reader reader = mock(SegmentDirectory.Reader.class);
+    when(reader.toSegmentDirectory()).thenReturn(segmentDirectory);
+
+    FSTIndexHandler handler = createHandler(segmentDirectory);
+
+    assertThrows(UnsupportedOperationException.class, () -> handler.needUpdateIndices(reader));
+  }
+
+  @Test
+  public void testNeedUpdateThrowsForMultiValueColumn()
+      throws Exception {
+    SegmentDirectory segmentDirectory = mockSegmentDirectoryForNewColumn(FieldSpec.DataType.STRING, true, false);
+    SegmentDirectory.Reader reader = mock(SegmentDirectory.Reader.class);
+    when(reader.toSegmentDirectory()).thenReturn(segmentDirectory);
+
+    FSTIndexHandler handler = createHandler(segmentDirectory);
+
+    assertThrows(UnsupportedOperationException.class, () -> handler.needUpdateIndices(reader));
+  }
+
+  @Test
+  public void testUpdateIndicesCreatesNewFstIndexForNewColumn()
+      throws Exception {
+    File indexDir = buildMinimalSegment();
+    try {
+      TableConfig tableConfig = new TableConfigBuilder(TableType.OFFLINE).setTableName("testTable_OFFLINE").build();
+      Schema schema = new Schema.SchemaBuilder().addSingleValueDimension(COLUMN, FieldSpec.DataType.STRING).build();
+      FieldIndexConfigs fieldIndexConfigs =
+          new FieldIndexConfigs.Builder().add(StandardIndexes.fst(), new FstIndexConfig()).build();
+
+      try (SegmentDirectory segmentDirectory = new SegmentLocalFSDirectory(indexDir, ReadMode.mmap);
+          SegmentDirectory.Writer writer = segmentDirectory.createWriter()) {
+        // Writer extends Reader, so it can be used for both the pre-check and the update.
+        FSTIndexHandler handler = new FSTIndexHandler(segmentDirectory, Map.of(COLUMN, fieldIndexConfigs),
+            tableConfig, schema);
+        assertTrue(handler.needUpdateIndices(writer), "New column should require FST index creation");
+        handler.updateIndices(writer);
+      }
+
+      assertTrue(new File(indexDir, COLUMN + V1Constants.Indexes.LUCENE_V912_FST_INDEX_FILE_EXTENSION).exists(),
+          "FST index file should be created for a newly configured column");
+    } finally {
+      FileUtils.deleteQuietly(indexDir.getParentFile());
+    }
+  }
+
+  private static FSTIndexHandler createHandler(SegmentDirectory segmentDirectory) {
+    FieldIndexConfigs fieldIndexConfigs =
+        new FieldIndexConfigs.Builder().add(StandardIndexes.fst(), new FstIndexConfig()).build();
+    return new FSTIndexHandler(segmentDirectory, Map.of(COLUMN, fieldIndexConfigs),
+        mock(TableConfig.class), mock(Schema.class));
+  }
+
+  private static SegmentDirectory mockSegmentDirectory(String column) {
+    SegmentMetadataImpl segmentMetadata = mock(SegmentMetadataImpl.class);
+    when(segmentMetadata.getName()).thenReturn("testSegment");
+    when(segmentMetadata.getTotalDocs()).thenReturn(1);
+    when(segmentMetadata.getAllColumns()).thenReturn(new TreeSet<>(Set.of(column)));
+
+    SegmentDirectory segmentDirectory = mock(SegmentDirectory.class);
+    when(segmentDirectory.getSegmentMetadata()).thenReturn(segmentMetadata);
+    when(segmentDirectory.getColumnsWithIndex(StandardIndexes.fst())).thenReturn(Set.of(column));
+    return segmentDirectory;
+  }
+
+  /**
+   * Mocks a {@link SegmentDirectory} where {@code COLUMN} has no existing FST index but is
+   * configured to receive one — used by the unsupported-operation tests.
+   */
+  private static SegmentDirectory mockSegmentDirectoryForNewColumn(
+      FieldSpec.DataType dataType, boolean hasDictionary, boolean isSingleValue) {
+    ColumnMetadata columnMetadata = mock(ColumnMetadata.class);
+    when(columnMetadata.getColumnName()).thenReturn(COLUMN);
+    when(columnMetadata.getDataType()).thenReturn(dataType);
+    when(columnMetadata.hasDictionary()).thenReturn(hasDictionary);
+    when(columnMetadata.isSingleValue()).thenReturn(isSingleValue);
+
+    SegmentMetadataImpl segmentMetadata = mock(SegmentMetadataImpl.class);
+    when(segmentMetadata.getName()).thenReturn("testSegment");
+    when(segmentMetadata.getTotalDocs()).thenReturn(1);
+    when(segmentMetadata.getAllColumns()).thenReturn(new TreeSet<>(Set.of(COLUMN)));
+    when(segmentMetadata.getColumnMetadataFor(COLUMN)).thenReturn(columnMetadata);
+
+    SegmentDirectory segmentDirectory = mock(SegmentDirectory.class);
+    when(segmentDirectory.getSegmentMetadata()).thenReturn(segmentMetadata);
+    when(segmentDirectory.getColumnsWithIndex(StandardIndexes.fst())).thenReturn(Set.of());
+    return segmentDirectory;
+  }
+
+  private static SegmentDirectory.Reader mockReaderWithFstBuffer(SegmentDirectory segmentDirectory,
+      String column, PinotDataBuffer buffer)
+      throws Exception {
+    SegmentDirectory.Reader reader = mock(SegmentDirectory.Reader.class);
+    when(reader.toSegmentDirectory()).thenReturn(segmentDirectory);
+    when(reader.getIndexFor(column, StandardIndexes.fst())).thenReturn(buffer);
+    return reader;
+  }
+
+  private static SegmentDirectory.Writer mockWriterWithFstBuffer(SegmentDirectory segmentDirectory,
+      String column, PinotDataBuffer buffer)
+      throws Exception {
+    SegmentDirectory.Writer writer = mock(SegmentDirectory.Writer.class);
+    when(writer.toSegmentDirectory()).thenReturn(segmentDirectory);
+    when(writer.getIndexFor(column, StandardIndexes.fst())).thenReturn(buffer);
+    return writer;
+  }
+
+  /** A {@link PinotDataBuffer} whose first int is the legacy native FST magic value. */
+  private static PinotDataBuffer legacyNativeBuffer() {
+    PinotDataBuffer buffer = mock(PinotDataBuffer.class);
+    when(buffer.size()).thenReturn((long) Integer.BYTES);
+    when(buffer.getInt(0)).thenReturn(LEGACY_NATIVE_FST_MAGIC);
+    return buffer;
+  }
+
+  /** A {@link PinotDataBuffer} whose first int is NOT the legacy native FST magic value. */
+  private static PinotDataBuffer nonLegacyBuffer() {
+    PinotDataBuffer buffer = mock(PinotDataBuffer.class);
+    when(buffer.size()).thenReturn((long) Integer.BYTES);
+    when(buffer.getInt(0)).thenReturn(0);
+    return buffer;
+  }
+
+  /**
+   * Builds a minimal v1 segment with a single dictionary-encoded STRING column ({@code COLUMN}).
+   *
+   * @return the segment directory (tempDir/segmentName)
+   */
+  private static File buildMinimalSegment()
+      throws Exception {
+    File tempDir = new File(FileUtils.getTempDirectory(), "fst-index-handler-test-" + System.nanoTime());
+    FileUtils.deleteQuietly(tempDir);
+    if (!tempDir.mkdirs()) {
+      throw new IOException("Failed to create temp directory: " + tempDir);
+    }
+
+    Schema schema = new Schema.SchemaBuilder().addSingleValueDimension(COLUMN, FieldSpec.DataType.STRING).build();
+    TableConfig tableConfig = new TableConfigBuilder(TableType.OFFLINE).setTableName("testTable_OFFLINE").build();
+
+    SegmentGeneratorConfig config = new SegmentGeneratorConfig(tableConfig, schema);
+    config.setOutDir(tempDir.getAbsolutePath());
+    config.setSegmentName("fst-handler-test-segment");
+    config.setSegmentVersion(SegmentVersion.v1);
+
+    List<GenericRow> rows = new ArrayList<>();
+    for (String value : List.of("apple", "banana", "cherry")) {
+      GenericRow row = new GenericRow();
+      row.putValue(COLUMN, value);
+      rows.add(row);
+    }
+
+    SegmentIndexCreationDriverImpl driver = new SegmentIndexCreationDriverImpl();
+    driver.init(config, new GenericRowRecordReader(rows));
+    driver.build();
+
+    return new File(tempDir, "fst-handler-test-segment");
+  }
+}